This invention relates to automatic control systems for traction vehicles and has particular application to rapid transit or other railway vehicles.
Automatic train operation (ATO) control systems have been developed to improve the operation of rapid transit systems and to minimize the opportunity for accidents caused by human error. In general, ATO systems include signal devices positioned along a fixed guideway, such as a railway track or monorail system, for providing information to vehicles on the guideway as to the position of the vehicles and the velocity at which the vehicles are to proceed. Communication receivers on the vehicles receive the information from the wayside signal devices and convey it to the ATO control circuitry which controls power and braking to regulate the velocity of the vehicles.
An exemplary ATO system is shown in U.S. Pat. No. 3,334,224 issued on Aug. 1, 1967 to R. K. Allen and I. W. Lichtenfels and assigned to the General Electric Company. That patent discloses an analog ATO system, i.e., an ATO system in which values are determined by the magnitude of continuously variable voltage and current signals.
Although ATO systems for controlling the velocity of a vehicle are not unusually complex, the addition of control circuitry to stop the vehicle at a predetermined position without excessive deceleration or jerk can result in a quite complex arrangement. Furthermore, the implementation of position stop circuitry using analog techniques--which require multiple potentiometers for setting voltage levels and rely on capacitor energy storage--may become, in addition to being complex, excessive in physical size. For example, many additional components may be needed if the position stop circuit is required to adjust the stopping point of the lead vehicle in a train of vehicles which can vary from one to ten vehicles in length. In addition, the diameter of the steel wheels on the vehicles change with service and the system must compensate for that change in computing the position of the train with respect to the stopping point.